Modern electrical power distribution systems supply power to a large number of electrical loads, such as residences, factories or businesses. The power consumed by each electrical load is separately measured by an electrical metering device, such as an induction or electronic type watthour meter. Many electrical power distribution systems include tens of thousands or even hundreds of thousands of metering devices.
Induction type watthour meters have historically been utilized to measure electrical energy consumption. Induction type watthour meters include an aluminum disk driven as a rotor of a small induction motor by an electric field at a speed which is proportional to the electric power consumed by the load. Geared dials, or cyclometer disks, integrate the disk's motion to indicate the total energy consumed, conventionally measured in kilowatt hours.
Recently, an increasing number of electronic type watthour meters have been employed to measure electrical energy consumption since they are capable of measuring several quantities in addition to tabulating the kilowatt hours of power consumed by the corresponding load. For example, electronic type watthour meters can measure the power factor, kilovolt amperes ("KVA"), and reactive volt amperes of the power consumed. The increased metering flexibility and capacity provided by electronic type watthour meters is due, at least in part, to the electronic acquisition, integration and processing of the measured electrical consumption of the load by, for example, an electronic processor or controller.
The total electrical power demand upon most power distribution systems is cyclical throughout each day with one or more peaks in the demand for electrical energy. The cyclical electrical energy demand is relatively consistent such that the peaks in electrical energy demand occur at substantially the same time each day. Likewise, the off-peak time periods also occur at relatively the same times of each day. Thus, many suppliers of electrical power charge more for electrical energy consumption during the peak periods of time during a day than during the off-peak periods to reflect the increased cost of supplying the power during the peak periods.
Due to their electronic processing capabilities, electronic type watthour meters readily provide time of use metering. Time of use metering separately tabulates the electrical consumption of the load during distinct, predetermined periods of time. Electronic time of use watthour meters, therefore, may measure the electrical energy consumption separately during the predetermined off-peak and peak periods of time. Separate billing rates may thereafter be applied to the electrical consumption during those periods of time by the suppliers of the electrical power.
Electronic type watthour meters typically include a number of programmed instructions and predefined values stored in a non-volatile memory device associated with the electronic controller or processor for controlling the meter's operation. For example, the particular times of day defining off-peak and peak periods may be stored. The instructions and values are originally stored during the initialization of the electronic watthour meter. In many instances, the instructions or values must be modified after the electronic watthour meter has been installed, such as, for example to modify the times of the day defining the off-peak and peak periods for a electronic time of use watthour meter.
There are several methods of communicating with electronic type watthour meters so as to modify the pre-programmed instructions or values. For example, the modified instructions and values may be manually entered into the memory of the electronic watthour meters. Alternatively, some electronic watthour meters include an optical communications port. For these meters, the modified instructions or values may be downloaded, via an optical probe, to the electronic watthour meter.
In addition, other electronic watthour meters include a radio frequency ("RF") receiver or transceiver. For these meters, the revised instructions or values may be broadcast, such from a central station or radio tower, to the electronic watthour meters. Still other electronic watthour meters communicate with a central station via the telephone lines. These electronic watthour meters typically include a modem adapted to receive signals from and transmit signals via the telephone lines.
Power line communications may also be utilized to reprogram electronic watthour meters. A typical power line communication system, such as that illustrated in U.S. Pat. No. 4,749,992 to Fitzemeyer, includes a central control station, typically referred to as a system control center, which transmits signals to one or more radio towers. The signals may be transmitted to the radio tower by RF transmission or by cable television or telephone lines or by a satellite or microwave link. Each radio tower, in turn, rebroadcasts the signals to a plurality of nodes, such as by RF transmission. Each node is typically a remote local relay module associated with a distribution transformer. Each relay module then transmits the signals via the consumer electronics bus ("CEBus") to the electrical metering devices connected between the secondary side of the associated distribution transformer and the electrical loads.
The CEBus includes the power lines extending from the distribution transformer to the electrical loads, i.e. residences or businesses, as well as the electrical wiring within the residences or businesses. As known to those skilled in the art, signals are transmitted via the CEBus according to a predefined format or protocol. One standard protocol for CEBus signals is established by the Electronic Industries Association of Washington, D.C. in a publication entitled "EIA Home Automation System (CEBus) EIA IS-60" and published October, 1992.
The electronic type watthour meters coupled to the electrical loads of the distribution transformer include a modem for receiving and translating the signals transmitted via the power line. The modem thereafter provides the translated signal to the controller or processor for immediate execution.
One power line communications system is the UCNet.RTM. system marketed by General Electric Company, assignee of the present invention. The UCNet.TM. system is described and illustrated in a brochure entitled "GE UCNet System" by GE Meter and Control of Somersworth, N.H. which bears document number GEA 12091 9/91 7M. The UCNet.TM. system is also described in a publication entitled "Engineering Presentation To AEIC/EEI Meter and Service Committees" by GE Meter and Control which bears document number GET-6638.22 9/91 (3M).
In addition, some electrical power distribution systems include combinations of the various methods for reprogramming an electrical type watthour meter. Thus, a first group of electrical metering devices may be reprogrammed, for example, via power line communication while a second group of meters may be reprogrammed via optical communications.
Since a typical power distribution system includes tens of thousands or even hundreds of thousands of electronic metering devices, it has not been possible to simultaneously reprogram each electronic metering device regardless of the method by which the electronic watthour meters are reprogrammed. Accordingly, there may be significant differences in operation and performance between the electronic metering devices which have and those which have not been reprogrammed. These operational and performance differences will continue until all of the meters have been reprogrammed.
In many instances, it would be desirable for the revised instructions or values to become effective in each meter of the power distribution system simultaneously. For example, the modified instructions or values may redefine the off-peak and peak time periods. It would thus be desirable that the revised off-peak and peak time periods be simultaneously effective in each electronic metering device so that the electrical consumption of each load is allocated and billed identically in each metering device. Although it would be desirable to simultaneously reprogram each electronic metering device of a power distribution system, the present methods for reprogramming electronic metering devices impose significant delays in the times at which the modified instructions or values are effective in the metering devices.